1. Field of the Invention
The present invention relates generally to mobile computer networks, and more specifically to a mobile computer network which is composed of a plurality of subnetworks of different functionality for mobile hosts.
2. Description of Related Art
A computer network for mobile computing is described in a paper "A New Mobile-IP Scheme-Architecture and Evolution Scenario", Kazuhiro Okanoue et al., the Institute of Information Processing, the Fiftleth National Meeting, IU-7, 1995. This mobile computer network is composed of a plurality of subnetworks. To allow mobile hosts to perform session in any of the sub networks with fixed hosts, two addresses arc assigned to each mobile host. These arc a subnetwork-independent logical identifier and a subnetwork-dependent geographical identifier, whereas fixed hosts arc assigned only one address, i.e., logical identifier. Because of the difference in address assignment, a functionality known as "agent" is required for each subnetwork to establish sessions between mobile hosts and fixed hosts. The subnetwork which is identified by the logical address (identifier) of a mobile host is the home subnetwork of the mobile host and the agent of this subnetwork is known as a "home agent", and the agent of a subnetwork to which the mobile host is temporarily attached is known as a "current agent". The agent of a subnetwork provides multicasting of beacon packets for collecting location data from mobile hosts attached to it and provides database management of logical and geographical identifiers collected from the mobile hosts. The database is used to encapsulate a data packet with a geographical identifier if the destination is a mobile host.
However, all subnetworks are not necessarily provided with an agent facility. If a mobile host is moved to an agentless subnetwork, no session cannot be established with any of fixed hosts.